Equal arm balance



Sept. 4, 1951 w. c. GRIFFIN EZQUAL ARM BALANCE 5 Sheets-Sheet 2 Filed 001:. 8, 1947 Wil Iom C. Grffn,

INVENTOR.

Sept. 4, 1951 w. c. GRIFFIN EQUAL ARM BALANCE 5 Sheets-Sheet 5 Filed Oct. 8, 1947 Wi!lom C. Grffin, INVENTOR. BY%W Sept. 4, 1951 w. c. GRIFFIN 2567161 EQUAL ARM BALANCE F'iled Oct. 8, 1947 5 Sheets-Sheet 4 Wilhom C. Griffin,

' INVENTOR.

P 1951 w. c. GRIFFIN 2,567,161

EQUAL ARM BALANCE Filed Oct. 8, 1947 5 Sheets-Sheet 5 William C. Grfiin INVENTOR.

Patented Sept. 4, 1951 UNITED STATES PATENT OFFICE EQUAL ARM BALANCE William C. Griffin, Newport, Del.

Application October 8, 1947, Serial N0. 778,630

13 Claims. 1

This invention reiates to improvements in balances for comparing weights or weighing artic1es, and more particularly it relates to improvements in analytical baiances such as are used for analytical and assay work.

Balances of this kind have been designed so as to have a high sensitivity and in general are constructed with a balance beam hung at its middle upon a knife edge and. having saaie pans hung from its end.knife edges, a11 enclosed within a case to protect the movab1e parts from disturbance from air currents. T maintain sensitivity, it is essental that these beam knife edges, as well as the p1anes which support the knife edges during weighing operations, be sharp and polished. T0 substantially avoid damage to them during weighing operations, a beam arrest system is commonly provded that disengages. these balance beam knife edges from their respective supporting planes. Thus; whenever a weight is. added to or removed from the baiance pans, the beam is arrested, thereby disengaging the knife edges from the supporting p1anes.

This procedure is tedions and time-consuming and the sensitvity of the baiance is materia1ly reduced by the frequent engagement and disengagement of the beam knife edges with the supporting planes.

It is an object of my nvention to provide an improved balance having novelmeans for eifecting preliminary weighing operations without utilizing the sensitive knife edges in the pre liminary weighing operations.

Another object of my invention is to devise said means in the form of a liftmechanism capab1e of being moved to disengage the sensitive knife edges from their supporting p1'anes whiie Figure 1 is a front elevational view of an analytical baiance embodying my invention;

Figure 2 is a longitudinal partially sectional view on an enlarged sca1e of a portion of the balance shown in Figure 1.

Figure 3 is a bottom plan view of the portion of the balance shown in Figure 2.

Figure 4 is a front elevation partly in sectionof the interior member of the portion of the balance shown in Figure 2.

Figure 5 is a top plan view of the porton of the balance shown in Figure 4.

Figure 6 is a side eievation partly in seotion of the assembly shown in Figure 4.

Figure 7 is a front elevation of another interior portion of the balance as shown in Figure 2.

Figure 8 is a side elevation of the parts shown in Figure 7.

Figure 9 is a front elevational view partly in section similar to that of Figure 2 except that the parts are shown in a different operating position.

Figure 10 is a top plan view of the portion of the balance as shown in Figure 9.

Figure 11 is a detailed view partiy in seotion of a portion of the balance shown in Figure 9.

Figure 12 is a detailed view showing the position of some of the parts which do not appear in Figure 9.

Figure 13 is a front eievational view partly in secton similar to that shown in Figures 2 and 9 except that the parts are shown in sti11 a difierent position.

Figure 14 is a detailed view showng the posi tion of some of the parts which do not appear in Figure 13.

Figure 15 is a front e1evation of a portion of another type of ba1ance embodying the present invention.

Figure 16 is an end view partly in seotion of the balance portion shown in Figure 15.

Figure 17 is a top plan view of a portion of the balance shown in Figure 15.

Figure 18 is a front elevation showing the operation of the balance portion shown in Figure 15 when in a different position.

Like numerals designate corresponding parts in 2111 the figures of th drawings. 'Ihe particuiar analytical balance shown in Figure 1 is se- 1ected merely for the purpose of illustrating my invention and. is a laboratory balance, the same being enclosed within a conventional draft proef casing lil erected upon a oase H and having a sliding door 12 to give access to the enciosed weighing mechanism.

Referring particularly to Figures 1 to 14 of the rawings, the baianee includes a support comprising base II, central tubuiar body portion or column l3 mounted on the base, sad column having at its upper end an arm l4. Arm |4 carries a central knife edge supporting plane I5 adapted to support the halance beam I6 hy its central knife edge I'l. Counterweight supporting means and mass (te he weghed) supporting means are carried at opposite ends of the halance beam, and in the type of halance illustrated these means comprise, respectively, pans [8 and I8a, suspended from the opposite ends of the beam hy familiar terminal knife edges (of which the right hand knife edge 45 appears in Figures 2, 9, 11 and 13, it heing understood that there are correspondng parts not shown in these figures on the left hand side of the halance) on the beam ancl corresponding terminal knife edge supports or planes 46 and 25a in the stirrups [9 and l9a.

The halance beam |6 may he of any preferred construction and may he provided with the usual adjustments and adjusting means employed for zero setting and increasing the sensitivity of the balance. The beam is provided with a long pointer 2, traversing graduations on a suitable index memher 2 I, to indicate the periods of oscillation of the moving parts of the balance durng weighing operatons and show when it comes to po1se.

The halance is provided with swingng stirrup support levers 22 and 22a, which are jointly pivoted at their inward ends on the pin 23 in the back of the upper portion of the central tubular body portion or column l3, as shown in Figure 10, and in line with the line of contact of the central knife edge I. These levers are provided with adjustahle pins 21 and 2a having upper ends which are hall or point shaped and which are in turn adapted to fit into members 28 and 28a (which may he flat, oupped, grooved or conically shaped) on the beam to lift the beam when the levers are raised. These levers carry, at their free ends, V-shaped stirrup supports 41 and 41a, which When raised lift the cross hars 48 and 48a of the stirrups to therehy lift the knife eolge hearings of the stirrups 0 of the corresponding knife edges (such as right hand knife edge 45) of the beam. As the beam ll is itself capahle of heing lifted hy the stirrup levers, it can he seen that the stirrup support levers, when in raised position, take the loads of the various parts off of the knife edges. In Figures 1 to 12 the halance is shown with the knife edges so dsengaged from their supporting planes.

Conventional halances generally comprise a beam arrest mechanism which may he movecl to lift the halance beam, disengage its central knife eolge hearing and hold the beam in rigid arrest position. Generally such beam arrests operate through the stirrup support levers and lift these levers to disengage not only the central knife edge hearing, hut also the terminal knife edge hearmgs.

Conventional weighing operations on such halances constitute placing the object or material to be weighed on the left pan and one or more weights of approximate measure on the right pan while the halance beam is in lifted arrest position. The beam arrest mechanism is then lowered and the halance is thus in weighing position with the beam free to oscillate about the horizontal central knife edge as fulcrum. The relation of the weight of the mass to he weighed and the counterweight employed is ohserved hy noting the angular swing of the beam about its fulcrum, and is ordinarily indicated by th position, relative to the index memher, of the pointer attached to the beam. If it is ohserved that the weights placed on the right pan are too light 01 too heavy, the beam arrest is raisec, the weights on the right pan are exchanged for lighter or heavier weights, and the beam arrest is again lowered. This operation is very tedious and timeconsuming and must he continued until balance has been attained. Moreover, the frequent engagement of the knife edges with the knife edge supports or planes causes a dulling and oftentimes chipping of the knife edges and their supporting planes, which greatly impairs the sensitivity of the balance.

According to the present invention, I provide a novel lift mechanism which may be used to disengage the knife edges during the course of weighing operations, and in addition permits an ex pedient preliminary weighing of the object or material to be weighed when the knife edges are disengaged.

In the embodiment of the invention shown in Figures 1 to 14 this is accomplished hy providing a second beam 24 having a hollow central portion 29 and pivotally hung by means of a central hearing in the upper end of the central hollow portion on hearing pin 3. As shown the center line of this second central hearing is substantially in alignment with the line of contact of the central knif edge hearing and ths construction constitutes a preferred emhodiment of the invention. However, if the second central hearing is to he located at a position not substantially in alignment with the line of contact of the central knife edge hearing, the center line of the second central hearing and the line of contact of the said central knife edge hearing should nevertheless he suhstantially within a single vertical plane.

As shown in detail in Figures 4 and. 5 the outer ends of the pin 30 are held in opposite sides of the hollow portion of the beam and the central portion of the pin 30 passes through a hole in the upper end of the slide memher 3! which serves as hearing support for pin 30. Slicle memher 31 is adapted to he raised and lowered to lift and lower the beam 24 and is provided at its lower end with suitahle mechanism, hereinafter more fully described, for this purpose.

Beam 24 is located helow the swinging stirrup support levers 22 and 22a, said beam when in raised position contacting the lower ends 25 and 25a of the lift guide pins 26 and 2611 to lift the stirrup support levers.

As shown in Figures 4 and. 6 the slide memher 3I consists of a rod of circular or other suitahle cross section and is adapted to he moved vertically upward or downward within the column by means of a turning movement of thumh wheel shaft 32 shown in Figure 3. This turning movement is translated into a vertical movement through the agency of a collar 33, having loeated adjacent to its circumference, 2. pin 34 adapted to fit into slot 35 in the link 36 which is pivotally connected at its upper end to the lower end of slide memher 3| hy means of pin 37.

As shown in Figure 13 beam 24, slide memher 3I, and link 36 are in a lowered position with pin 34 in slot 35. When the collar 33 is turned clockwise, the link slide memher and beam are raised hy pin 34 until the pin reaches the highest position as shown in Figure 9. Further clockwise movement of the collar 33 disengages pin 34 from slot 35, the pin moving into the position shown in Figure 2. This latter movement of pin 34 from the position shown in Figure 9 to the position shown in Figure 2 may be used to actuate some ether portion of the mechanism, as for example,

.be provided at its lower end with a curved elongated slot 39 through which passes a sutable flxed guide pn 40. A spring: 4| suitably connected to the base of the balance andto thelower endof link 36 retains the beam 24, slide member and link in uppermost position ater pin 34 has disengaged from slot 35.

As can be seen in Figures 1 and 2 When the beam 24, slide member 3! and link 36 are in uppermost position and the pin 34 has passed out of engagement with the slot 35, the beam 24 has lifted the swinging stirrup support levers 22 and 22a whic h have in turn lifted the beam -so that all of the beam knife edges are disengagedfrom their Supporting Tbearings, the principal weigh-t of the stirrup support levers and the balance beam |6 being carried by beam 24 at 25 and 25a to the sides of the hearing 30. However, the beam. 24, instead of being in -a fixed rigid position, as in the case of a conventional balance in arrest position, is supported by the central hearing 3:0 and is capable of pivoting about this hearing pin as shown in dotted lines in Figure 2.

As the pin 30 and the pin 23, upon which the inner ends of the sti-rrup support levers 22 and 22a are jointly pivoted, are each in approximate alignment with the disengaged central knife edge i'l, the .en tire assembly, comprisingthe beam 24, the stirrup support levers 22 and 22a, the beam IS, the stirrups 13 and lila, and the suspended paus I0 and Hier, is supported byand capable of swinging about the pins 30 and 23 as ndicated in dotted lines in Figure 2. In addition cross bars 48 and 48a of the stirrups 19 and |3a are free to swing on and are in hearing engagement with the V-shaped members 41 and 41a in the outer ends of the stirrup support levers, 'Ihis permits a preliminary weighing to be aceomplished with all knife edges disengaged, with pins 30 and 23 serving as the fulcrum and principal hearing support, and with the cross bars 48 and 48a tand corresponding v-shaped members 4! and 4111 serving as outer pan support bearings. After the;preliminary weighing is accomplished the beam 24 may be 'lowered to the position shown in Fg-ure 13 with the resultant lowering of stirrup support levers 22 and 22a and the placement of the knfe edges upon their bearings in position for final weighing. While, in the embodirnent of the invention shown, the fulcrum and principal hearing support (When the knife edges are disengaged) is in the form of the hearing pins 30 and 23, it will be understood that either or both of these pins -may be in the form of more elaborate bear-- ings such as roller bearings, hall bear-ings, or the like. Likewise, the outer bearings between the. cross bars 46 and 46a and V-shaped members 41 and 41a may be jeweled or otherwise refined if so desired.

When the lift mechanism is to be operated to engage or disengage the knife edge, it is preferable that beam 24 be held in a rigid horizontal (true arrest) position, and in accordance with an embodiment of the inventon means are provided for locking the said beam in such position.

In the embodiment of the nvention shown in Fgures 1 to 14, this loc'king arrest means comprises a second slide member in the form of a sleeve 38 about the slide member 3 said sleeve having at the upper end thereof oppositely positioned lugs 42 and 42a adapted to fit into locking engagement with the lower end of the hollow risid horizontal position. The sleeve 38 is meunted withn column. [3 and is adapted to. bemoved vertcally upwardly or downwardly within the celumn l 3.

As shown in Figures 2, 7, and 8, the sleeve 3.0 is raised and lowered by means of a link member 43. The lower end of link 43 is pivoted to and operated by the pin 34 on the collar 33 on the thumb wheel shaft 32. The upper end of link 43 is in the form of a yoke attached at its upper end. by means of pins 44 and 44a to the lower end of the sleeve 38. The lower portion of link 43 is in the form of a U-shaped channel within which the link 36 of the slide member 3I can operate without interfering with the link 43.

When carrying out a weighing operation in .accordance with this preferred exnbodirnent of my invention, the balance is first leveled and adjusted to equilibrum after which the balance is placed in arrest and the beam lift mechanism being in the position shown in Figure 9 withthe central balance knife edge H and the terminal knife eclges (sueh as 45) out of engagement with their respective supporting planes (such as 46) as shown in Figures 11 and 12. It will also be noted that in this position, link 36, pivoted to slicle member 3I, and link 43, pivoted to sleeve 38, are in vertical alignment and that pin 34 to which link 43 is pivoted at its -lower endis abutting the inner end of slot 35. The object or material to be Weighecl is nowplaoed upon the balance pan 1811 and the approximate Weights to counterbalance the object or material to be weighed are placed upon the balance pan 18. The thurnb wheel shaft 32 is then turned clockwise with the result that pin 34 lowers link 43 and sleeve 38 until the lugs 42 and. 4211 are out. of engagement with the -beam 24, as shown in Figure 2. During this phase of the operation, the collar carries the pin 34 out of slot 35, the slide member 3! and its link 36 remaining stationary and being stopped by pin 40 in the lower end of slot 39, this position of link 36 being maintained by spring 4l. As a result, the

beam 24 is free to oscillate with the balance beamand the swinging stirrup levers 22 and 22a while the oentral knife edge of the beam as well as the terminal knife edges are still disengaeed. from their respective supporting planes. Thus, without engaging the beam knife eclges with the knife edge planes, weights of appreciable size may be added to or removed from the balance pan until approxirnate balance is attained. Since there is no need to arrest the beam with eaeh addition or removal of weights during this preliminary weighing operation, the weighing operation is expedited and the weight of an ojbject or material can be approximatecl withinclose 1i1nits. After the weight of the object 01 material being weighed has been preliminarily deterrnined, the pin 34, sleeve 33, lugs 42 and 4211, and link 43 are raised to the position shown in Figu-re 9 by turning the thumb wheel shaft 32 counterclockw-ise for a distance sufficient to permit the pi-n 34, attachecl to the collar 33, to ully engage the slot In this position the links 36 and 43 are brought into alignment, the lugs 42 and 42a of the sleeve 38 are within the hollow portion 251 of the beam 24 for a distance sufieient to look the beam 24 in horzental position with the result that the centra. l:nife edge I and the terminal knife eclges 45 and 45a rernain dsengaged frorn the-ir respective supporting .p1anes and the balance is in conventional or true arrest portion 29 of the beam 24 to held the latter in 7" position.

To complete the weighng operation, the beam lift assemhly is lowered to the position shown in Figures 13 and 14, whereby the central knife edge l1 and the terminal knfe edges, 45 and 45a engage their respective supporting planes. T accomplish this, the thumh wheel shaft 32. is turned Counterclockwise so that pin 3-4 lowers links 36 and 43, thus lowerng slide members 31 and 36. Guide slot 35 retains link 36 in such position that pin 34 is held so as to fully engage slot 35. EX- perience has shown that in many instances, after preliminary weighing, halance of the object 01 material being weighed may be attained in the final phase of the weighing operation only by use of suitable rider or chain weight (not shown).

Figures 15 to 18 illustrate another type of balanceconstruction emhodying the present inve'ntion.

As shown in these figures, swinging stirrup support levers 12 and 12a have bearings at their inner yoke-like ends where they are pivoted on journals of aligned pins 49 and 50 held in the upper ends of a support comprising rigid member 51 mounted on column I. The front of member 51 is provided with an arm carrying a central knife edge supporting plane 52 for a halance beam not shown. The stirrup support levers 12 and 12a. are provided with pins to engage the halance beam, and with V-shaped stirrup supports at their outer ends in the same manner as support levers 22a and 22 in Figure 1. Like the operation of the halance of Figure 1, upward. movement of the stirrup support levers 12 and 12a lifts the central knife edge of the balance beam from its supporting plane and also lifts the knife edge hearings of the stirrups (not shown) ofi the corresponding knife edges of the beam.

In the emhodiment of the invention shown in Figures 15 to 18, however, the lift mechanism comprises two levers 53 and 53a fulcrumed on hearing rods 54 and 54a, respectively. The outer ends of these rods are held in the lower corners of two oppositely positioned plate-like mernhers 55 and 56, each of which is provided at its upper encl with a hearing 55a and 5641, these hearings heing respectively journaled on aligned pins 50 and 49. Fins 49 and 50 are preferahly substantially in alignment with the line of contact of the halance beam knife edge hearing of which supporting plane 52 is shown in Figures 16 and 17.

Memhers 55and 56 are rigidly connectecl hy suitable means such as plates 68 and 69 extending hetween them and form a second beam pivotally hung on bearings 55a and 56a.

It will he understood that while the stirrup support levers and the second beam are shown as pivoted on the same hearing pins, separate hearing pins could be providecl. However, the center line of the hearing upon which the second beam is hung, if not suhstantially in alignment with the line of contact of the central knife edge hearing, should be suhstantially within the same vertical plane as the line of contact of the central knife edge.

The inner ends of levers 53 and 53a are opp0sitely offset and are provided with hearings 58 and 59, respectively, carried hy the hearing pins 60 and 6I at the lower ends of links 62 and 63. These links are carried at their upper ends by the outer ends of pin 64 the center of which is a journal carried hy a hearing in the upper end of slide member 65. This slide member extends downwardly through column 5I and may "he raised or lowered hy suitahle mechanism not shown, at the hottom of column 5l.

A second slide member comprising sleeve 66 within column 5! and about slide member 65 is also adapted to he raised and lowered hy means of suitahle mechanism at the bottom of column 5l. sleeve 66 carries at its upper enda T-shaped member 61, the cross of the T heing provided at each of its opposite ends with an upwardly projecting lug, 10 and 10a, adapted to fit into locking engagement with corresponding recesses in the center of the lower edges of members and 56. In Figure 18 recess 11 in plate 55 is shown out of engagement with lug 10, whereas in Figures 15 and 16 the lugs are in locking engagement with plates 55 and 56.

As shown in Figures 15 and 16 slide member 65 is in its lower position with pin 64 in alignment with pins 49 and 50. Through pin 64, links 62 and 63, and hearing pins and 61, slide member holds the inner endsof levers 53 and 53a, in downward position, with the result that the outer ends of these levers, which fulcrum about rods 54 and 54a, have engaged and lifted swinging stirrup support levers 12 and 12a. When so lifted the stirrup support levers in turn lift the halance beam and the stirrups (not shown) so that all of the knife edge hearings are disengaged.

As shown in Figures 15 to 17 sleeve 66 is in raised position with lugs 10 and 10a in, and in locking engagement with, the corresponding recesses in the lower edges of platelike members 55 and 56. As a result the entire lift mechansm is in rigid arrest position.

By lowering sleeve 66 and T-shaped member 61 to the position shown in Figure 18, lugs10 and 10a are disengaged from the recessesin members 55 and 56 with the result that the beam formed hy members 55 and 56 is capable of swinging about the heaiings 55a and 56a from which it is pivotally hung. The prncipal weight of the and 12a and the stirrups are free to swing on and. are in hearing engagement with the V- shaped memhers at the outer ends of these levers, a preliminary weghing may be accomplisheci with all sensitive knife edges dis'engaged and with aligned pins 49, 50 and 64 serving as the fulcrum and principal hearing support anclwth the V-shaped memhers at the outer ends of levers 12 and 12a serving as outer pan support bearings.

When the weight of the object or material has been preliminarily determined and the oscilla tions indicatecl in Figure 18 cease, the beam and arrest mechanism reach a suhstantially horizontal position. Sleeve 66 and T-shaped member 61 are then raised to engage and look members 55 and 56 in rigid arrest position. slide member 65 is then raised to lift the inner ends of levers 53 and 53a through pin 64, links 62 and 63 and hearing pins 60 and 61. By this movement the outer ends of levers 53 and 53a are lowered and in turn low er stirrup support levers 12 and 12a. As with the lowering of stirrup support levers 22 and 22a, of the balance shown in Fguie 1, the lowering of stirrup support levers 12 and 12a permits the central knife edge of the beam and the terminal knife edges to engage their respective supporting planes, aftervvhich final precisin weighing can be accompiished.

It will be understood that the portion of the lift mechanism of the present invei1tib'n that is free to oscillate during the weighing operation should be constructed so that the parts on one side of the central hearing pin, or pins, counterbalance the parts on the other side of the sai'd pin, or pins, and that said. portion of the lift mechanism ma3 be provided with one or more adjustable weights, such as those custmaiily found at the outer ends of balance beams, for the purpose of adjusting the balance of the lift mechanism so that the pointer 20 is at zero position when the lift mechanism is in pre1irninary weighirig position and the pans are empty.

In the enibodiments of the inventir'1 shown in the drawings, the lift mechanism is actuated by and. comprises a slide member movably mbuntd Within the column, this location being convenient' and highly suitable. However it is to be understood that the lift mechanism "inay oe located entirely outside of the column ifso desied.

As the lift mechanism of the present invent-on has as a primary purpose the conservation of the senstive knife edges and their supporting planes, it has been il-lustrated as applied t analytical balances havng stirrup support levers which in themselves tend to prevent impairment of the sensitivity of the knife edge bearings. However, the lift mechai1ism of the present invention and comprising a second beam pivotally mounted for the purpose of condcting a prelminary weighing may be applied to other types of balances.

The second beam can be employed to lift and carry only the mass supporting means and the counterweight supporting means leaving the balance beam in its normal position if desiied. In the str1icture illustrated in Figures 1 to 14, th;is is r'eadily accomplished by retraction of the adjustable pins '21 and 21a in their respectve threaded mounts so that the pins do not erigage the members 28 and 28:: of the balance beam when the arrest structure is in fu11y l evated position. The stirrup supports 4"! and l=7a engage and lift the cross bars 48 and 48a of the stirrups thus picking up the load of the mass and counterweight supporting ineans and transmitting the load to the second beam.

Alternatively, the second beam can be operated to lift the balance beam albne without disen'gag ing the mass and coiuterweight supportin'g means from the balance beam. For exarnpie; in the structure illustrated in Fi-gures 15 to 18, this can be accomplished by the removal of the threaded stirrup support studs from the opposite ends of the stirrup support 1evers T2 and 12a leaving the balance beam lfting pins alone on the said levers. 'Ihe same effect can be attained in the structure illustrated in Figures 1 to 14 by elevating the adjustable pins '21 and '2Ia so that on lifting the arrest structu're they engage the members 28 and 28a and. so lift the balance beam before the stirrup supports 41 and 41a erigage the cross bars 48 and 48a of the stirrups thus prevnting the engagement and Iiftng of the stirrups.

In the specification and claims refeience is made to knfe edge plane. It is 'to be u'ndei- 10 stood that these terms are terrns of the balance art and mean the surface aclapted to contact the knife edge during the weighing operation which surface need not be geometrically plane as it is frequently concave or in the form of a tio i1gh.

Having ful1y described my invention, what I claim is as follows:

1. In a balance, having a support, a balance beam a balance beam hearing having knife edge and kriif edge plane elements one of which is carried by said support and the other is carried by said balanc beam intermediat its ends, mass to be weighed supporting means vertically disengageably carried by said balance bearn at one side of 'said hearing, and counterweght supporting means vertically disengageably carried by said balance beam at the other side of said hearing; preliminary weighing means including a second beam, a. second beaiiiig or said second. beam intermeciate the ends thereof, members for engag ing and lifting said supporting means to disengage the same from said balance beam, means for transmitting weight between the said membrs and the respective pposite ends of said second beam, and selectively operable means for moving said memlors into engaging and lifting relation with said supporting mans.

2. A balaneas set forth in claim 1 and wherein the said second hearing is in substantial alignment with the line of contact of the knfe edge hearing.

3. In a balance having a support, a balance beam, a balan'ce be"am hearing having knife edge and knife edge plane elemehts one of which is carried by said support and the other is carried by s'aid balance beam intermediate its ends, mass to be wighed supp0iting means carried by said balahce beam at one side of said hearing, and counterweight supporting means carried by said ba1ance lam at the other side of said balance beam; prelirn'inary weighihg means inclucling a second beam, a second hearing for slid second. beam intermediate the ends thereof, 1novable mear for engaging and lifting said balance beam to disengag'e the knife edge hearing thereof, means for trans'n1ittihg Weight frorn said movabl means to the said setzond beam through positions on opposite sides of said second hearing to permit the second beam to function as a prlminary balance bam, and selectively operable means for moving said movable means into engaging and lifting relation with the firs't Said balance beam.

4. A ba1ano as set forth in claim 3 and wherein the sai 's'eciid hearing is in substantial alignnent with the line of contact of the knife edge berihg, when the balance beam is in lifted position.

5. A balance having a support, a balance beam, a balance bem hearing h'aving knife edge and knife edge plane elements, one of which is carried b5 said support and the other is carried by said balance bam iritermediate its ends, a weighing panstirrup at each end of said balance beam, a stiriup knfe edge bearng for each of said stirips, each bea'r'ing c0mprising knif edge and knife ege plane elements, one of which is carried by the stirrup and the other is carried by saidba lance beam at an end thereoi, swnging. Stirrup support levers pivotally mounted at their inner ends.on b'earings substantially in algnment with the Tine of contact of said balance beam knife edge bearing and. engageable with said stirrups to lift the Same and disengage the respective stirrup knife edge bearings, means connected to said stirrup support levers to engage and lift said balance heam to disengage the knife edge hearing thereof when said levers are swung. to engage said stirrups, a preliminary balance heam. a hearing for said preliminary balance heam located intermediate the ends thereof and in substantial alignment with the line of contact of the said balance heam knife edge hearing, and selectively operahle means for moving said preliminary balance heam to h'ring a portion thereof lying at one side of its hearing into operating engagement with one of the swinging stirrup support levers and a portion lying at the opposite side of its hearing into contact with the other of the swinging stirrup support levers to swing the said stirrup support levers to engage and lift the stirrups and the balance heam to disengage the respective knife edge hearings thereof and to transmit the weight to the preliminary balance heam for a preliminary weighing.

6. In a balance, a support comprising a tubular column, a balance heam, a balance heam hearing having knife edge and knife edge plane elements one of which is carried hy said support and the other is carried hy said balance heam intermediate its ends, mass to he weighed supporting means mounted at one end of said balance heam, counterweight supporting means mounted at the other end of said balance heam, a second heam, a hearing for said second heam located intermediate the ends thereof and in suhstantial algn- 1nent with the line of contact of the said balance heam knife edge hearing, a slide memher movahly mormted in said tuhular column, selectively operable means or raising and lowering said slide memher, and balance heam engaging means connected to said second heam and operahle hysaid slide memher to lift said balance heam to disengage the balance heam knife edge hearing and place the weight of said balance heam and the supporting means mounted thereon on the second heam in preliminary weighing relation.

: 7. A balance as set forth in claim 6wherein the said second heam has a hollow central portion and the hearing for said heam is supported on the upper portion of said slide memher, the balance -urther having a second slide memher m0vahly mounted in said tuhular column and engageahle in one position with the hollow central portion of said second heam to look. the same,

and selectively operahle means for moving said second slide memher into and out of engagement with the second heam.

8. In a balance, a support comprising a tuhular column, a balance heam, a balance heam hearing having knife edge and knife edge plane elements one of which is carried hy said support and the other is oarried by said balance heam. intermediate its ends, a stirrup at each end of the balance heam, a hearing for each of said stirrups each hearing having knife edge and. knife edge plane elements, one of whichis carried hy an end of the balance heam and the other is carried hy the stirrup, swinging stirrup support levers pivotally mounted on their inner ends on hearings substantally in alignment with the line of contact of said balance heam knfe edge hearing and engageahle with said strrups to lift the same and disengage the respective stirrup knife edge hearings, said levers also heing engageahle withsaidhalance heam to lift and disengage the knife edge bearing thereof when said levers are swung to engage said stirrups, a second heam, a first slide memher mounted for vertical movement within said tubular column, a pivotal connection bein substantial alignmnt with the line of contact of the said balance heam knife edge hearing, said second heam heing carried into weighing engagemert with said swinging stirrup support levers when said first sliding member is lifted to swing said levers to cause them to lift the stirrups and the balance heam, a second slide memher mounted for vertical movement within said tuhular column, cooperating dsengageahle locking means on said second heam and on said second slide memher to prevent oscillation of the second heam when the second slide memher is in-lifted position, raising and. lowering mechanism for selectively raising and lowerin said first and second slide memhers together in one selected operation and for lowering said second slide memher while leaving the first slide memher in raised position in another selected operation.

9. In a balance, a support comprising a tuhular column, a balance heam, a balance heam hearing having knife edge and knife edge plane elements, one of which is carred hy said support and the other is carried hy said balance heam intermediate its ends, mass supporting means mounted on one end of said balance heam, counterweight supporting means mounted on the other end of said balance heam, a balance heam lift mechanism comprising a second heam pivotally hung on said support hy means of a second central hearing suhstantially in alignrnent with the line of contact of the balance heam knife edge hearing, balance heam lifting levers fulcrumed on said second heam at points to the sides of said second central hearing, and a slide memher movahly mounted within said column, the upper end of said slide memher heing connected to the inner ends of said levers wherehy downward movement of said slide memher raises the outer ends of said levers to lift the said balance heam, the principal weight of the mass supporting means and the counterweight supporting means heing carried through said levers at the ulcrums thereof on the said second heam when said balance heam is in lifted position, said second heam heing capahle of oscillating ahout said second central hearing to permit a weighing operation when the said slide memher is in raised position.

10. A balance as set forth in claim 9 wherein the said second heam has a recess hetween the fulcrum of the balance heam lfting levers, the balance further having mounted in said tuhular column a second slide memher carrying a projection engageahle in one position with the recess of the said second heam to look the same, and selectively operahle means for moving said second slide member and its projection into and out of engagement with the second heam.

11. In a balance co-mprising a support, a halance heam, a sensitve weighing hearing having disengageahle hearing elements carried respectievly hy said support and said balance heam, and mass to he weighed supporting means and counterweight supporting means carried hy said balance heam at opposite sides of said hearing; a preliminary weighing heam, a support for said prelimnary weighing heam, cooperating preliminary weighing hearing elements carried respectively hy the preliminary weighing heam and hy its support, and selectively operahle means including said last mentioned support for disengagng said sensitive weghing hearing elements and mposing the weight of said supporting means on said preliminary weighng heam to per mt a. preliminary weighng operation upon the preliminary weighing hearing elements.

12. In a balance comprising a senstive weighing balance beam, a support for said beam, a knife edge be'aring element centrally located on said beam, a cooperatng knife ed-ge hearing element on sad support, mass to be weghed supportng means disengageably carried at one end of sad beam, and counterweght supporting means disengageably carred at the other end of said. beam; a prelimnary weighing beam, a support for a prelminary weghng hearing, a preliminary weghing hearing having cooperating elements carried respectvely by the said preliminary weghing beam and the last said support, and selectively operable means includng the last said support for disengaging both of said supporting means from the sad sensitive weighing beam and mposing the weight of said supporting means onto opposte ends of sad prelimnary weighing beam.

13. A balance having a senstve weghing beam provided with a disengageable fine weighing centrai hearing, beam 1ftin elements engageable wth said weghng beam at opposite sdes of said hearing, a member rgdly supporting said lfting elements when in engagement with said. weighing beam, said lifting elements and said member constituting a prelmnary weighing beam, a pvota1 central support for the preiimnary weighing beam, and selectively operable means or moving said 1iftng elements into engagement with sad senstive weighng beam t0 lift the same and disengage the fine weighng hearing, the sensitive weighing beam beng carried by the preliminary weighing beam in the lifted position of the former whereby a prelminary weghng operaton can be performed.

WILLIAM C. GRIFFIN REFERENCES CITED UNITED STATES PA'IENTS Name Date Thompson Feb. 3, 1942 Number 

